Origen, one of the wisest and most interesting of the early theologians, had an ingenious theory about the obvious discrepancies in the Bible. If one discovered a difference in, for example, the genealogies of Jesus as they appear in Matthew’s and Luke’s Gospels, he argued that these were hermeneutic trip wires deliberately inserted by the holy spirit to make the reader think that bit harder about the New Testament’s other meanings – symbolic, ethical and allegorical – rather than the merely literal.

Unfortunately, most readers threw their considerable intellectual efforts into elaborate literal interpretations designed to iron out the inconsistencies, with all the fervour of Star Trek fans circa 2003 coming up with theories about why Koloth, Kor and Kang had smooth foreheads in the original TV series and bony ridges in Deep Space Nine. Nowhere does this nimbus of lore, inference, legend, presumption and legerdemain accrete more creatively than around the 12 apostles.

Tom Bissell’s book is consistently fascinating about the stories that crept as inexorably as lichen over a gravestone around the people closest to Jesus. The travelogue elements make for a pleasant hike out of the archive and into surprising places – one might expect Rome and Jerusalem, but his quest involves trips to Spain and France, Turkey and Russia, India and Kyrgyzstan. Acts 1:8 has the apostles being told to be witnesses “both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth”. They seem to have made a fair fist of it, and even if they didn’t actually do it personally, they certainly did so in story.

Even in setting his itinerary, Bissell is confronted with a problem. Is Bartholomew, mentioned by Mark, Matthew and John, the same person as Nathanael, mentioned in Luke and Acts? Is Thaddeus identical with Jude, the “son of James”, or Jude “not Iscariot”, both, or neither? Is Simon, whom Matthew calls “the Cananean” the same Simon whom Luke calls “the Zealot”? Given he includes Paul – the self-proclaimed “Apostle to the Gentiles” – it seems a bit rum not to include Matthias, who is elected to replace Judas Iscariot. It would at least have meant a trip to either Ethiopia or Caucasian Georgia.

A major part of the book involves the controversy around James the Lesser; who might be James the Just and might be James, the son of Alphaeus, and might be James, the brother of Jesus, mentioned in First Corinthians, Acts and Galatians. The idea that Jesus had siblings has always been problematic, and some of the cerebral gymnastics to get around the issue are grounded in much later doctrine: if Mary is perpetually virgin, then figures such as James and Jude are half-brothers, or cousins. Bissell concentrates more on the disputes between “Jewish” Christianity and Paul’s mission to the gentiles. James is the figurehead of those who believe that new followers of the Way must also follow the Mosaic law; and any subterranean or suppressed history seems more enticing. The idea of a “Jewish Christianity” being written out of history by perfidious Pauline Christians must be set against the real extirpation caused by the Roman destruction of the Temple in the year 70CE, which had profound ramifications for both Judaism and early Christianity.

In elegantly unpicking the minutiae, Bissell sometimes forgets to stand back and look at the wider picture. It is undergraduate fun to quibble over whether Judas hanged himself or fell and exploded in a suppurating mass of corruption. It is much more difficult to pose the big questions. Given that the Gospels do give neat and memorable pictures of individuals – the vertically challenged tax gatherer Zacchaeus, the aged Simeon and Anna in the Temple, Mary Magdalene – it is exceptionally odd that we get so little about the apostles. The Gospels often introduce seemingly extraneous detail: why do we need to know that Simon of Cyrene was “the father of Alexander and Rufus”? They are the strangest mixture of art naïf and profound, philosophical narrative. There is something ludicrous about the various apocryphal Acts and Gospels, with their talking dogs and dastardly wizards; yet, such documents came about only a few centuries after the individual they purportedly describe died. To take an equivalent, there are 600 years between the death of Alexander the Great and the romantic flimflam of The Alexander Romance.

Detail of Saint Mary Magdalene kneeling before a priest from
Life of Saint Mary Magdalene fresco. Photograph: Elio Ciol/Corbis

Bissell begins the book, fairly, by saying that he was brought up within the church and leaving it has not stifled his fascination with it. That said, the tone is sometimes slightly supercilious, offset by gap year harrumphs about having diarrhoea, getting hammered and being ripped off by locals. Some of the writing strains towards profundity – the “zirconium eyes” of a drunk, the “watermelon light” over the Tiber, “merkins of shrubbery”. And whatever one’s thoughts about believers being naive or doltish, there is something ungenerous about referring to Russian Christians as “old, blobby parishioners … staggering on varicose legs” or drawing attention to the “poached, sun-swollen bags under her eyes” of an Irish widow who wants to see the supposed tomb of John.

These hazy saints, flickering at the edge of history, almost dare us to imagine. And sometimes, though the author may not approve, the results are sublime. Take GK Chesterton expanding on Peter – “a shuffler, a snob, a coward – in a word, a man … the historic Christian church was founded on a weak man, and for that reason it is indestructible. For no chain is stronger than its weakest link”. Or Jorge Luis Borges riddling through his “Three Versions of Judas”, or Hölderlin’s throat-catching “Patmos”. The apostles remain strange inspirations, and the debunking of daft claims about them was always old hat.